Machines have been used to rotate a reel for the winding-up or paying-off an elongated material, for example, a cable. In industrial applications, the rotational speed of and torque applied to the reel can be varied throughout the winding-up or paying-off process in correspondence with the amount of cable on the reel. With a full reel of cable, each rotation of the reel equates to a greater length of cable compared to a near empty reel due to the greater diameter of cable on the full reel. To wind-up or pay-off at a constant rate, the rotational speed of the reel can decrease as the cable gets wound up or it can increase as the cable is paid-off. Also, the required rotational torque increases with the greater amount of cable on the reel. Many machines have the capability to wind-up and pay-off reels of multiple sizes, as the reels can have reel cores and reel flanges of varying diameters and axial lengths.
There can be safety issues associated with winding-up and paying-off cable from a reel, since operators typically assist in the winding-up or paying-off process. For example, when winding cable onto a reel, an operator typically loosely holds on to the cable near the reel to direct the cable on to the reel in order to insure an even cable traverse. The operator's care is required when an uneven cable traverse has occurred, since the operator is needed to redirect the cable to fill the uneven portion to compensate for the uneven traverse. As the operator redirects the cable, a safety problem can occur if the operator gets caught up with the cable as it is being wound onto the reel. If this happens, the operator may be pulled over the reel and can be injured.
There have been a number of devices designed to solve some of the safety concerns. One safety solution involves using photo-detectors to create a beam of light adjacent to the reel. This solution is unsatisfactory because a light beam directly in front of the reel may be broken by an operator during the normal winding-up or paying-off process, thereby unnecessarily shutting down operations. Also, this solution can fail to detect an operator's presence in the area between the flanges of the reel, since the light beam generator and reflector sense only the area outside of the flanges of the reel.
Another inadequate solution uses a floor mat having sensors in it for detecting the operator's presence on the mat. When the operator steps off the mat, the motor powering rotation of the reel is shut down. A disadvantage of the floor mat approach is that the reel may be traversed over the floor mat requiring the operator to move out of the way. Another solution uses photo-sensors and multiple beams of light crossing the area where the operator stands. These solutions are problematic because they restrict the position of the operator to a given area. As the operator may occasionally need to move up and down the length of cable in order to properly wind-up or pay-off the cable, restricting the position of the operator is undesirable. Further, the known solutions are impractical because they require the operator to notify/disable the system when the operator must leave the mat/sensor area. Additionally, the known solutions are not flexible enough to adjust to various reel sizes and wind-up and pay-off locations. Another disadvantage of the known safety systems is that they are not easily adjustable to guard the safety of an operator over a wide range of reel sizes.